(a) Technical Field
The present invention relates to a (halo)silicate-based phosphor and a manufacturing method of the same.
(b) Background Art
A technology for manufacturing a white light emitting diode (LED), which has recently been actively researched all over the world, is largely divided into three categories.
First, a white light emitting device can be manufactured by mounting red, blue and green light emitting diode chips in one package, and controlling the respective chips. Second, a white light emitting device can be manufactured by coating a phosphor having red, blue and green luminescent properties on a UV light emitting diode chip. Third, a white light emitting device can be manufactured by coating a phosphor having a yellow luminescent property on a blue light emitting diode chip.
Among such conventional technologies, a white light emitting device using the respective red, blue and green light emitting diode chips has a problem that its operating voltage is non-uniform, and each chip's output varies according to an ambient temperature. This changes a color coordinate, and thus makes it difficult to uniformly mix respective colors with each other. Thus, in such a white light emitting device, it is difficult to obtain a pure white light. Also, in consideration of the electrical properties of respective chips or respective light emitting diodes, additional operating circuits are required. Further, such circuits are required to be controlled. Thus, the technology has a disadvantage in that the manufacturing process is complicated, and also it is inefficient to express a high-brightness white light in view of power consumption.
In order to complement the above described problems, manufacturers currently coat a phosphor, in which phosphors having red, blue and green luminescent properties are mixed in a predetermined ratio, on a UV light emitting diode chip, or coat a phosphor having a yellow luminescent property on a blue light emitting diode chip in manufacturing of a white light emitting device. This method requires a simple process and has an economical advantage, unlike the above mentioned method using the respective red, blue and green light emitting diode chips. Furthermore, in this method, an additive color mixture can be achieved by using light emitted from a phosphor. Thus, there is an advantage in that it is easy to adjust a color coordinate, and various colors can be expressed.
Especially, there are a lot of patent applications on a method which uses europium as an activator on a blue light emitting diode chip, and a silicate-based phosphor containing an alkaline earth metal. For example, Korean Patent Laid-Open Publication Nos. 2003-0067609, 2006-0015036, and 2002-0025696 disclose a method of expressing a white color by using a gallium nitride (GaN) LED chip emitting a blue light, and a YAG:Ce3+ (Yttrium Aluminum Garnet) phosphor emitting a yellow light, mainly in a band of 460 nm. Also, Korea Patent Application Publication No. 2006-0111116A discloses a phosphor having Formula of (Sr1-x-yAx)2SiOz:Euy (A represents at least one kind of alkaline earth metal selected from the group consisting of Mg, Ca, Sr, Br and Ra, 0≦x<1, 0.001≦y≦0.3, and Z represents an integer of 1 to 5). Such a phosphor emits yellow light with an absorption peak in a range of about 300 nm to 480 nm, and an emission peak in a range of about 500 nm to 680 nm especially when 0≦x≦0.35. In such methods for expressing white light by coating a phosphor on a light emitting diode chip with a short wavelength range, an excitation wavelength of the phosphor has to exactly correspond to a light source wavelength. If they do not correspond to each other, the phosphor has low excitation efficiency, and thus has a very low brightness. This causes a serious deviation in a color coordinate. Also, a green light emitting silicate-based phosphor may be used to realize a light emitting device, in which generally, a Eu2+ ion is used as an activator, and a green phosphor having a Formula of A2SiO4:Eu2+ is used (in Formula, “A” represents a compound of two kinds or more selected from the group consisting of “Sr”, “Ba”, “Ca”, “Mg”, etc., and another ion than Eu2+ may be co-doped). However, a conventional green light emitting phosphor has a problem that its brightness is reduced due to irregular morphology such as the generation of a large amount of residue during a heat treatment process, and the synthesis of fluorescent particles having irregular sizes. Furthermore, there is a problem that the brightness is reduced according to the kind of a conventionally used compound in a case where the ion is doped in a heat treatment environment.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.